[LeetCode] Reverse Linked List II

Reverse a linked list from position m to n. Do it in-place and in one-pass.

For example:
Given 1->2->3->4->5->NULL, m = 2 and n = 4,

return 1->4->3->2->5->NULL.

Note:
Given m, n satisfy the following condition:
1 ≤ m ≤ n ≤ length of list.

[Solution].java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode reverseBetween(ListNode head, int m, int n) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        ListNode start = head;
        ListNode last = head;
        ListNode front = head;
        ListNode rear = head;
        boolean fromBegin = false;
        if(m == 1){
            fromBegin = true;
        	rear = head.next;
        }
        while(true){
            if(m > 2) start = start.next;
            else if(m == 2){
                last = start.next;
                front = start.next;
                if(n > 2) rear = front.next;
                else break;
            }
            else{
                if(n > 1){
                    ListNode temp = rear;
                    rear = rear.next;
                    temp.next = front;
                    front = temp;
                }
                else if(n == 1){
                    if(!fromBegin) start.next = front;
                    else head = front;
                    last.next = rear;
                }
                else break;
            }
            m--; n--;
        }
        return head;
    }
}